Which drug is commonly used to treat petit-mal (absence) seizures?

• A. Ethosuximide
• B. Phenytoin
• C. Valproic acid
• D. Gabapentin

Answer: (A)

Absence seizures originate from abnormal rhythmic activity in the thalamocortical network, driven in part by T-type calcium channels. Ethosuximide works by selectively blocking these T-type calcium channels in thalamic neurons, which reduces the low-threshold calcium currents that sustain the spike-and-wave discharges seen in absence seizures. By dampening this specific pathway, it effectively prevents the brief lapses in consciousness that define petit-mal seizures, making it the treatment of choice for this seizure type. Other options target different mechanisms or have broader effects; phenytoin and gabapentin are not effective for absence and can be ineffective or even worsen it in some cases, while valproic acid can help many generalized seizures but carries more risks and is not needed here when focusing on absence alone.